Method to determine optimal micro-bump-probe pad pairing for efficient PGD testing in interposer designs

ABSTRACT

The present disclosure relates to a method of routing probe pads to micro-bumps of an interposer. An interposer is provided having target micro-bumps and probe pads. The probe pads are initially unassigned. Target micro-bump locations and probe pad locations are obtained. Possible route assignments from the probe pads to the target micro-bumps are obtained. Costs are developed for the possible route assignments at least partially according to the target micro-bump locations and the probe pad locations. Final assignments are selected from the possible assignments according to the costs.

BACKGROUND

Semiconductor device fabrication is a process used to create integratedcircuits that are present in everyday electrical and electronic devices.The fabrication process is a multiple-step sequence of photolithographicand chemical processing steps during which electronic circuits aregradually created on a wafer composed of a semiconducting material.

The electronic circuits include various components, such as transistors,capacitors, resistors, and the like. The components need to beelectrically connected to each other and/or other components, such asbond pads. Various techniques are utilized for electrically connectingthe components, such as conductive vias, lines, channels, interconnects,and the like.

One mechanism to facilitate electrical connection between components isto utilize an interposer. This is a layer that does not contain anyactive transistors, only interconnects. The interposer is generally usedfor providing connections to multiple die or chips.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram illustrating a method for performing routing ofan interposer layer in accordance with this disclosure.

FIG. 2 is a flow diagram illustrating a method for performing routing ofan interposer layer in accordance with this disclosure.

FIG. 3 is a diagram of an example interposer in accordance with thisdisclosure.

FIG. 4 is a flow diagram illustrating a method of partitioning aninterposer in accordance with this disclosure.

FIG. 5A is a diagram illustrating partitioning of an interposer into aplurality of regions in accordance with this disclosure.

FIG. 5B is a diagram illustrating merging overlap regions of aninterposer in accordance with this disclosure.

FIG. 5C is a diagram illustrating a merged region of an interposer inaccordance with this disclosure.

FIGS. 6A to 6D illustrate a graphical approach to identifying low costroutings or pairings between micro-bumps and probe pads in accordancewith this disclosure.

FIG. 7A is a diagram illustrating another mechanism to select probe padand micro-bump pairs in accordance with this disclosure.

FIG. 7B is a flow diagram illustrating a method of selecting probe padmicro-bump pairs in accordance with this disclosure.

FIG. 7C is example pseudo code for implementing a method of selectingprobe pad micro-bump pairs in accordance with this disclosure.

DETAILED DESCRIPTION

The description herein is made with reference to the drawings, whereinlike reference numerals are generally utilized to refer to like elementsthroughout, and wherein the various structures are not necessarily drawnto scale. In the following description, for purposes of explanation,numerous specific details are set forth in order to facilitateunderstanding. It may be evident, however, to one skilled in the art,that one or more aspects described herein may be practiced with a lesserdegree of these specific details. In other instances, known structuresand devices are shown in block diagram form to facilitate understanding.

Interposers are a mechanism to facilitate electrical connection betweencomponents. It is a layer comprised almost only of passive components orconnections and without active components, such as transistors.Interposers are generally used for providing connections to multiple dieor chips and typically have a first side with micro-bumps and a secondside with pads or probe-pads. The interposers include connections, alsoreferred to as interconnects, between the micro-bumps. Interposerstypically include three types of connections. A first type is a feedthrough, a second type is inter die connections, and a third type is afan out connection. The probe pads provide electrical connections to themicro-bumps.

For testing purposes, at least a portion of the micro-bumps have probepads associated therewith. This permits signals to be asserted tomicro-bumps at probe pads and allows analyzing resulting signals atother micro-bumps by using other probe pads. Thus, characteristics ofthe micro-bumps and interconnects can be analyzed or tested.

The connection between micro-bumps and/or probe pads is referred to aspairing. The paired connections have associated characteristics or costsassociated therewith. For example, the paired connections have loadingand capacitance due to the connections there between. Furthermore, itcan happen that at least portions of some paired connects are unused.

A net is one or more connections or pairings between micro-bumps, suchas for the three types of connections discussed above. A pairing orrouting is a connection from a probe pad to an associated micro-bump. Inone example, a fanout type net includes three micro-bumps connected toeach other and three probe pads, one for each micro-bump.

There is only a limited number of probe pads available. Generally, it isnot practical to assign a probe pad to every micro-bump in aninterposer. Further, the routing or pairing of the probe pads to themicro-bumps is important. Unnecessary lengths, for example, can degradethe testing of the micro-bumps and interconnects by introducingresistance and/or capacitance into the measurements. Thus, routing ofprobe pads to micro-bumps have associated costs and these costs, ifhigh, can negatively impact testing.

It is appreciated that a variety of pairings are possible to connectparticular or selected micro-bumps and probe pads. Multiple, variedpairings may result in needed or selected connectivity. However, theycan have very different costs.

Typically, selecting pairings for probe pads to micro-bumps is a manualprocess. A pairing is selected and evaluated. A person then decideswhether the pairings work well enough. If not, manual adjustments aremade. However, this approach is very time consuming and doesn'tnecessarily provide an improved or optimal pairing or routing of thenets. Further, the manual approach is realistically limited to smalldesigns only. Larger designs are too complex to be adjusted manually.Finally, the manual approach does not lead to product quality solutions.

This disclosure includes methods to find improved or optimal pairingbetween micro-bumps and probe pads. The improved or optimal pairing isreferred to as enhanced routing. The enhanced routing facilitatestesting of interposers by methodologies, such as pretty good die (PGD)testing. PGD testing is a methodology for passive interposer testing.For PGD testing, every net is typically connected to two probe pads viamicro-bump to probe pad connections. This permits front-side probing ofthe interposer.

FIG. 1 is a flow diagram illustrating a method 100 for performingrouting of an interposer layer in accordance with this disclosure. Themethod 100 provides enhanced routing of probe pads to micro-bumps. Themethod 100 facilitates testing of the interposer by mitigating routingcosts from the probe pads to the micro-bumps.

The method 100 begins at block 102, wherein interconnects, micro-bumplocations and probe pad locations for an interposer are obtained. Theinterposer is a layer comprised substantially of passive components,without active components, such as transistors. The interposer is usedfor providing connections to multiple die or chips. The interposer has afirst side with micro-bumps, referred to as micro-bumps, and a secondside with pads or probe-pads. The micro-bumps are typically coupled tocontacts on the multiple dies and provide connectivity to and betweenthe multiple dies. The probe pads permit external connections or probeconnections to the interposer and facilitate testing of the interposerand/or the dies connected to the micro-bumps.

There are three types of interconnects for the micro-bumps. A first typeis a feed through, a second type is inter die connections, and a thirdtype is a fan out connection. A feed through interconnect is a singleconnection through an interposer layer to/from a single micro-bumps. Aninter die interconnect is a connection of a number of micro-bumps frommultiple dies. For example, an inter die interconnect includes a firstmicro-bump associated with a first die and a second micro-bumpassociated with a second die. The first micro-bump and the secondmicro-bump have an interconnect there between. A fanout type is aninterconnect that connects a plurality of micro-bumps together. Forexample, three micro-bumps can be connected to each other by a singleinterconnect.

A number of probe pads are available on the interposer. Typically, thenumber of probe pads is substantially less than the number ofmicro-bumps. The probe pads have locations on the interposer.

Target testing nets are determined at block 104. A net is defined as aconnection or interconnect to one or more micro-bumps. A relativelylarge number of nets are present on the interposer. However, there areonly a limited number of the probe pads available. Thus, only a subsetof the available nets can be tested. The subset is referred to as thetarget nets. The total number of micro-bumps present in the target netsshould be less than or equal to the number of available probe pads.

The target nets or target interconnects are identified by impact orimpact factors. The impact factors include, for example, yield impact,likelihood of failure, and the like. For example, longer interconnectsare more likely prone to manufacturing failure and are typicallytargeted for testing.

The interposer is partitioned at block 106 into multiple regions. If theinterposer size is large enough, such as having over 1,000 micro-bumps,the interposer can be partitioned into multiple regions. If theinterposer size is not large, the interposer can be maintained as asingle region.

Partitioning the interposer can reduce computations and increaseefficiency of identifying routings between probe pads and the targetedmicro-bumps.

Routings or pairings for the probe pads and the target micro-bumps areassigned at block 108. The assignments include connections between theprobe pads and associated micro-bumps. The assignments are determined bydetermining costs between the probe pads and the micro-bumps andassigning the probe pad to micro-bump connections with lower or lowestcost.

The assigned routings for the probe pads and micro-bumps are performedat block 110. Thus, the probe pads are connected to the micro-bumps. Theroutings generally have a lower cost than routings from other mechanismsor methodologies. Furthermore, the interposer can be tested using PGD oranother testing mechanism.

It is appreciated that the method 100 can be performed multiple times toimprove the routings and lower the cost for the assigned routings.

FIG. 2 is a flow diagram illustrating a method 200 for performingrouting of an interposer layer in accordance with this disclosure. Themethod 200 is applicable to interposers of varied sizes. Further, themethod 200 facilitates device testing by providing routing top probepads that enhances semiconductor die testing mechanisms, such as prettyPGD testing.

The method 200 begins at block 202, where target testing nets of aninterposer are identified. The interposer is a layer comprisedsubstantially of passive components, without active components, such astransistors. The interposer is used for providing connections tomultiple die or chips. The interposer has a first side with micro-bumps,referred to as micro-bumps, and a second side with pads or probe-pads.The micro-bumps are generally coupled to contacts on the multiple diesand provide connectivity to and between the multiple dies. The probepads permit external connections or probe connections to the interposerand facilitate testing of the interposer and/or the dies connected tothe micro-bumps.

The interposer includes connections between the micro-bumps. TheInterposer includes three types of connections. A first type is a feedthrough, a second type is inter die connection, and a third type is afan out connection. These types of connections are described in greaterdetail above.

A net includes one or more micro-bumps and the interconnects therebetween. The interposer includes a relatively large number of nets. Someof the nets are more critical to device performance than others. Thenets that are more critical are selected or identified as target testingnets, also referred to as target nets. Furthermore, there are only alimited number of probe pads available for testing purposes. Therefore,only the higher priority nets are selected or targeted for testing.

The target nets can be identified by a suitable methodology ormechanism. In one example, nets with a high probability of defects areidentified as the target nets. In another example, nets having a sizegreater than a threshold value are identified as the target nets. Thesize refers to the number of micro-bumps present in the net. It isappreciated that other suitable methodologies are contemplated.

In one example, the target nets are selected according to availableprobe pads and impact factors. The impact factors include, for example,yield impact, likelihood of failure, and the like.

A determination is made on whether partitioning is needed at block 204.Generally, partitioning is needed when a size of the interposer exceedsa threshold value. The size of the interposer can be defined in terms ofgeographic area, number of nets, and/or number of micro-bumps present inthe interposer. In one example, the interposer size is the number ofmicro-bumps and/or interconnects present for the interposer.

If the method 200 determines that partitioning is needed, the method 200proceeds to block 206. The interposer is partitioned into overlappingregions at block 206 according to a partition or region size and anoverlap size.

The partition size is selected at block 214 and is a size that includesa suitable number of nets, but is small enough for relatively fastanalysis. The number of nets can be predetermined, such as 5. However,it is appreciated that the number of nets permitted per partition orregion can vary according to implementation.

In one example, designers specify and/or provide parameters to controlregions width and height. In another example, the width and height iscomputed according to the interposer size and the number of probe pads.

The overlap size is selected at block 216. The overlap size is selectedto facilitate efficient and low cost use of probe pads. The regionincludes the overlap size or overlap regions. In one example, designersspecify or provide parameters to set overlap region size. In anotherexample, the overlay size is determined according to correspondingregion/partition height and width.

Routings are assigned to micro-bumps and probe pads for each region atblock 207. The routings or pairings are assigned according to costfunctions for each possible connection for the micro-bumps within theregion. It is noted that overlap portions shared by different regionscan have different pairings or routings.

A variety of mechanisms can be utilized to assign routings between themicro-bumps and the probe pads. Several examples will be discussedbelow. However, generally, proposed or possible connections between themicro-bumps and probe pads are developed. Cost functions are generatedfor the proposed connections. The cost functions include one or more ofseveral factors including, but not limited to yield, routability,timing, power costs, and the like. In one example, the factors havevaried weights that are selected according to application requirements.For example, power costs or consumption could have a larger weight thentiming factors.

In one example, a lowest cost connection/routing for each pair isselected. In another example, a routing is selected for micro-bump toprobe pad as long as the cost is below a threshold value.

The routing assignments for overlap regions are merged at block 208. Theoverlap regions are also referred to as boundaries or boundary regions.The same overlap region can have multiple routing assignments. Thesemultiple routing assignments are analyzed to select or merge routingassignments for the overlap regions into final values or assignments.

In the event that partitioning is not performed, routings are assignedto micro-bumps and probe pads for the target nets of the interposer atblock 207. The operation is similar to that of the region assignments;however there is only one region and no overlap regions. Similar to theregions, the routings or pairings are assigned according to costfunctions for each possible connection for the target nets of theinterposer.

The region routing assignments and the overlap region assignments areperformed at block 212. In one example, these assignments are providedas final assignments for fabrication of the interposer. In anotherexample, these assignments are implemented in the fabrication of theinterposer.

The interposer, with the selected routing at block 212, typically has asubstantially lower cost than the interposer prior to performance of themethod 200. In one example, the interposer is then assembled with theselected connections.

Subsequently, testing can be performed on the interposer using the probepads to test the target nets.

FIG. 3 is a diagram of an example interposer 300 in accordance with thisdisclosure. The interposer 300 is provided as an example to facilitateunderstanding of the disclosure. The interposer is shown with a firstnet 310 and a second net 320. This example illustrates how to determineprobe pad and micro-bump sets to test each wire in the interposer 300.

The first net 310 includes micro-bumps b¹ ₁ and b² ₁. The second net 320includes micro-bumps b¹ ₂, b² ₂, b³ ₂ and b⁴ ₂. The notation used isb^(bump) ^(—) ^(id) _(net) _(—) _(id). The first net 310 is a two-pinnet and the second net 320 is a multi-fanout net. The first net 310could, for example, be an inter-die type connection.

For testing purposes, such as PGD testing, probe pads are assigned toeach of the micro-bumps to facilitate testing of interconnects betweenthe micro-bumps. A first pad-bump set is determined for the first net310 and includes {{P₁, b¹ ₁}, {P₃, b² ₁}}. A second pad-bump set isdetermined for the second net 320 and includes {{P₂, b⁴ ₂}, {P₄, b₁ ²},{P₅, b³ ₂}, {P₆, b² ₂}}.

The routings from the probe pads to the micro-bumps are shown in FIG. 3.These routings are obtainable using the methods 100 or 200 above tomitigate the cost functions for each routing and to enable testing ofthe interconnects of each net.

FIG. 4 is a flow diagram illustrating a method 400 of partitioning aninterposer in accordance with this disclosure. The method 400 can beincorporated into other methods of the disclosure, such as methods 100and 200.

The interposer is partitioned into sets of regions at block 402. Theregions include overlap regions that are shared by neighboring regions.In one example, the interposer is partitioned according to a partitionsize and an overlap size. The partition size sets the size for theregions. The overlap size is selected to encompass probe pads and/ormicro-bumps of the neighboring regions.

Probe pad and micro-bump pairs or sets are determined for a currentregion of the plurality of regions at block 404. FIG. 3, describedabove, provides an example of determining probe pad and micro-bump pairsor assignments for a region.

Possible assignments or routings are considered at one or more overlapregions for the current region at block 406. The assignments or routingsare also referred to as solutions. The overlap regions are regionsshared by neighboring regions. The overlap regions may have variedassignments by neighboring regions. For example, a probe pad for oneregion can be assigned or routed to a different micro-bump in a secondregion.

The assignments or routings are merged to final assignments at block408. The final assignments are also referred to as final solutions. Thefinal assignments are merged or determined according to cost factors,such as those described above.

Once complete, the method 400 proceeds to a next region at block 410 forsimilar evaluation. The blocks are repeated for the next and remainingregions of the interposer until final assignments are obtained for allthe regions.

FIGS. 5A, 5B and 5C are provided as a non-limiting example for themethod 400. It is appreciated that the method 400 operates on a varietyof interposers having varied configurations.

FIG. 5A is a diagram illustrating partitioning of an interposer 502 intoa plurality of regions in accordance with this disclosure. On a leftside, the interposer 502 is shown without partitioning. In the middle,the interposer 502 is shown partitioned into the plurality of regions. Acurrent region 504 is shown by the dashed lines. It is noted that anadjacent region shares an overlap region 506 of the current region, asshown in the right side and bottom side. Probe pad and micro-bump pairsor sets are determined for the current region 504.

FIG. 5B is a diagram illustrating merging overlap regions of aninterposer 502 in accordance with this disclosure. The overlap region506 of the current region 504 is compared with an overlap region of anadjacent region. It can be seen that the probe pads for the currentoverlap region and the adjacent overlap region are varied. An upperprobe pad is assigned to a micro-bump in the current region 504 and amicro-bump in the adjacent region. Further, a lower probe pad is unused.

FIG. 5C is a diagram illustrating a merged region of an interposer 502in accordance with this disclosure. Analysis is performed on the overlapregions to determine routing assignments. In this example, the upperprobe pad is assigned to the micro-bump in the adjacent region and thelower probe pad is assigned to the micro-bump in the current region 504.

There are several suitable mechanisms to determine routing assignmentsbetween probe pads and target micro-bumps. A first example, a graphicalapproach, in accordance with this disclosure is demonstrated in FIGS. 6Ato 6D. The graphical approach determines probe pad micro-bump pairs byusing a minimum cost, max flow algorithm for efficiency. The number ofedges is reduced by setting a search window. A directed edge is createdfrom each probe pad to micro-bump with an associated cost functionf(i,j).

Micro-bumps of a net are regarded as separate nodes. For each pad node,a directed edge to each bump node is created. The edge capacity u_{i,j}is set to 1 and the cost c_{i,j} is f(i, j, k). An edge from source toeach pad node is connected with c_{s, i}=0 and u_{s, i}=N (N>1); thesame setting is applied for the edge from each bump node to destination.However, in an interposer design, the total number of such edges couldbe large, directly solving this flow graph is time consuming.

To efficiently reduce the runtime, edge reduction is performed to removepotentially redundant edges. For each bump, we define a search windowfor the network-flow formulation. The pads outside the search window areignored; therefore, the flow graph size is greatly reduced. As shown inFIG. 6D, when constructing edges from pad nodes to a bump node, thoseedges with larger costs due to outside the window are pruned. Therefore,the total edge number is reduced, which makes the network-flow solvingmore efficient.

FIG. 6A illustrates the notation used to identify probe pads 602 andmicro-bumps 604. An example probe pad i is shown with a cost to anexample micro-bump j.

FIG. 6B illustrates an example set of micro-bumps 604 and probe pads602. Note that the probe pads 602 are not assigned to the micro-bumps atthis point.

FIG. 6C is a graph illustrating all possible probe pad to micro-bumpconnections. Each edge has an associated cost f(i,j). Thus, there are 6possible connections to each micro-bump for a total of 24 micro-bumps.

FIG. 6D is a graph illustrating a reduced number of edges for the probepad to micro-bump connections. A search window having a length and widthis established. The search window is positioned about each probe pad.Only connections to micro-bumps within the search window are added asedges to the graph.

For example, a search window for pad P1 only encompasses micro-bumps n¹₁ and n² ₁. Thus, the graph only has edges from P1 to micro-bumps n¹ ₁and n² ₁. The search window moves to each probe pad in order to form thereduced graph shown in FIG. 6D.

The reduced number of edges in the graph facilitates obtaining suitableassignments faster and with less computational complexity. Each edge isanalyzed for the cost and the lowest cost pair for each micro-bump isselected or assigned.

FIG. 7A is a diagram illustrating another mechanism to select probe padand micro-bump pairs in accordance with this disclosure. For thismechanism, a cost is determined for a current probe pad to availablemicro-bumps. The smallest cost path is selected and assigned. Then thenext probe pad is selected and costs are determined for the new currentprobe pad to the remaining micro-bumps. The mechanism continues untilprobe pads are assigned to all micro-bumps.

FIG. 7A shows a number of probe pads 702 and a number of micro-bumps704. In this example, the cost is selected as the distance d. Thus, forexample, P₁ is assigned to n¹ ₁ during the first iteration. P l isassigned to n² ₁ during a second iteration.

FIG. 7B is a flow diagram illustrating a method 710 of selecting probepad micro-bump pairs in accordance with this disclosure. The method 710elaborates on the example provided in FIG. 7A. The method 710 determinesa cost for available micro bump to probe pad pairs and assigns thelowest cost pair.

The method 710 begins at block 712 where probe pads and micro bumps areobtained for an interposer. In one example, the micro bumps are targetmicro bumps associated with target nets. The probe pads and the microbumps have locations or positions on an interposer.

A probe pad is selected and connection costs are determined foravailable micro bumps at block 714. It is appreciated that one or moreof the micro bumps can be previously assigned to a probe pad and,therefore, not one of the available micro bumps. The connection costsinclude one or more characteristics. In one example, the connection costis associated with distance from the selected probe pad to the availablemicro bumps.

The micro bump connection with the lowest cost is selected for theselected or current probe pad. The associated micro bump is removed fromthe list of available micro bumps. If additional probe pads remainunassigned, a next probe pad is selected at block 720 and the methodcontinues to block 714.

Otherwise, if all probe pads have been assigned micro bumps, the method710 stops. At this point, the selected connections can be routed fromthe micro bumps to the probe pads.

FIG. 7C is example pseudo code for implementing the above method 710 inaccordance with this disclosure. The pseudo code utilizes a set of probepads and a set of target testing nets. The target testing nets includetarget micro bumps.

It is appreciated that a longer wire tends to have a higher probabilityof manufacturing failure, such as from shorts, metal distortions, andthe like. The order of connections is determined by a net wire length asshown in lines 1-2. For each micro bump of a net, the distance betweenit and available probe pads is computed between it and available probepads. Based on the distance, the probe pad micro bump pair is chosen.Lines 7-10 show the assignment for a net in turn searches the priorityqueue of two micro bumps and marks the probe pad as unavailable if thedecision is made.

A third mechanism that can be used to assign pairs utilizes a formula.Integer Linear Programming (ILP) is utilized to formulate theassignments. A variable has an integer value from 0 to 1 to indicatewhether the probe pad micro-bump pair exists or not.

$\begin{matrix}\min & {\sum{{f\left( {i,j,k} \right)}x_{i,j}^{k}}} & \; \\{s.t.} & {{\sum\limits_{k}x_{i,j,k}^{k}} \leq 1} & \; \\\; & {{{\sum\limits_{i}x_{i,j}^{k}} = 1},} & {{\forall{k \in {K\mspace{14mu}{for}\mspace{14mu}{each}\mspace{14mu}{net}}}},}\end{matrix}$

where: x^(k) _(i,j): a candidate pad i is chosen to connect withmicro-bump k of net j

f(i,j,k): cost function for pad and bump

The cost function is utilized to obtain the routing assignments for theprobe pad micro-bump pairs.

The below table provides a comparison between a manual approach andmethods in accordance with this disclosure. It can be seen that themethods of this disclosure result in considerable reduction in timespent as compared with the manual approach. Additionally, the benefitincreases as the number of micro bumps and probe pads increases.Further, the lengths of the probe pad to micro-bump routing is alsoreduced substantially.

Manual Approach Method of this disclosure #bumps/ Spent WL Spent #padsWL (um) time WL (um) Reduction time 40/40 889.380 5 min 686.980 23% 0.11sec 80/80 1469.355 10 min 1117.585 24% 0.12 sec 200/200 3161.450 1 hour2155.715 32% 0.77 sec 400/400 8089.58 2 hour 6144.01 24% 0.75 sec500/500 11176.370 <0.5 day 9133.285 18% 1.17 sec 1000/1000 NA Almost14772.895 NA  0.5 sec impossible

It will be appreciated that while reference is made throughout thisdocument to exemplary structures in discussing aspects of methodologiesdescribed herein, that those methodologies are not to be limited by thecorresponding structures presented. Rather, the methodologies (andstructures) are to be considered independent of one another and able tostand alone and be practiced without regard to any of the particularaspects depicted in the Figs.

Also, equivalent alterations and/or modifications may occur to thoseskilled in the art based upon a reading and/or understanding of thespecification and annexed drawings. The disclosure herein includes allsuch modifications and alterations and is generally not intended to belimited thereby. For example, although the figures provided herein, areillustrated and described to have a particular doping type, it will beappreciated that alternative doping types may be utilized as will beappreciated by one of ordinary skill in the art.

The present disclosure includes a method of routing probe pads tomicro-bumps of an interposer. An interposer is provided having targetmicro-bumps and probe pads. The probe pads are initially unassigned.Target micro-bump locations and probe pad locations are obtained.Possible route assignments from the probe pads to the target micro-bumpsare obtained. Costs are developed for the possible route assignments atleast partially according to the target micro-bump locations and theprobe pad locations. Final assignments are selected from the possibleassignments according to the costs.

The present disclosure includes another method of routing an interposer.The interposer is provided having target micro-bumps and probe pads. Theprobe pads are initially unassigned. The interposer is divided intoregions according to a partition size and an overlap size. Regionassignments are developed from probe pads and target micro-bumps withineach region. Assignments for overlap regions are merged to develop finalassignments. The probe pads are routed to the target micro-bumpsaccording to the final assignments.

The present disclosure includes a method of routing an interposer. Theinterposer includes target micro-bumps and probe pads within a region.The region is one of a plurality of regions. Target micro-bump locationsand probe pad locations are obtained for the region. A reduced set ofroute assignments are identified according to a search window. Costs aredeveloped for the reduced set of route assignments. Region assignmentsare selected from the reduced set of route assignments.

While a particular feature or aspect may have been disclosed withrespect to only one of several implementations, such feature or aspectmay be combined with one or more other features and/or aspects of otherimplementations as may be desired. Furthermore, to the extent that theterms “includes”, “having”, “has”, “with”, and/or variants thereof areused herein, such terms are intended to be inclusive in meaning—like“comprising.” Also, “exemplary” is merely meant to mean an example,rather than the best. It is also to be appreciated that features, layersand/or elements depicted herein are illustrated with particulardimensions and/or orientations relative to one another for purposes ofsimplicity and ease of understanding, and that the actual dimensionsand/or orientations may differ substantially from that illustratedherein.

What is claimed is:
 1. A method of routing an interposer operating on acomputer mechanism, the method comprising: providing the interposerhaving target interconnects, micro-bumps and probe pads; obtainingtarget micro-bump locations for the target micro-bumps and probe padlocations for the probe pads; identifying possible route assignmentsfrom the probe pads to the target micro-bumps; developing costs for thepossible route assignments; selecting final assignments from thepossible route assignments according to the costs; and routingconnections from the probe pads to the micro-bumps according to thefinal assignments.
 2. The method of claim 1, further comprisingperforming pretty good die testing using the probe pads.
 3. The methodof claim 1, further comprising selecting the target micro-bumps from aplurality of micro-bumps present on the interposer.
 4. The method ofclaim 3, wherein the number of the target bumps is less than the numberof the plurality of micro-bumps.
 5. The method of claim 3, whereinselecting the target micro-bumps is performed according to impactfactors.
 6. The method of claim 5, wherein the impact factors includelikelihood of failure.
 7. The method of claim 1, the target micro-bumpsare associated with target nets.
 8. The method of claim 1, wherein thetarget micro-bumps are associated with target interconnects.
 9. Themethod of claim 1, wherein developing costs comprises using a linearalgorithm.
 10. The method of claim 1, wherein developing costs comprisesusing an edge directed graph.
 11. The method of claim 1, whereinidentifying possible route assignments comprises identifying allpossible route assignments from the probe pads to the targetmicro-bumps.
 12. The method of claim 1, further comprising partitioningthe interposer into a plurality of regions according to a size of theinterposer, each including an overlap region shared with another region.13. The method of claim 12, further comprising merging the overlapregions of the plurality of regions.
 14. A method of routing aninterposer operating on a computer mechanism, the method comprising:providing the interposer having target micro-bumps and probe pads;partitioning the interposer into regions according to a partition sizeand an overlap size; developing region assignments for probe pads andtarget micro-bumps within each region; merging assignments for overlapregions of each region to develop final assignments; and routingconnections from the probe pads to the micro-bumps according to thefinal assignments.
 15. The method of claim 14, wherein developing regionassignments comprises computing a cost connections between a currentprobe pad of the probe pads and available micro-bumps of the targetmicro-bumps and selecting a lowest cost connection.
 16. The method ofclaim 14, further comprising selecting the partition size and theoverlap size according to computational efficiency and merge quality.17. The method of claim 14, wherein partitioning the interposercomprises partitioning the interposer into a single region on a size ofthe interposer being below a threshold value.
 18. A method of routing aninterposer operating on a computer mechanism, the method comprising:providing the interposer having target micro-bumps and probe pads withina region; obtaining target micro-bump locations for the targetmicro-bumps and probe pad locations for the probe pads; identifying areduced set of route assignments from the probe pads to the targetmicro-bumps according to a search window; developing costs for thereduced set of route assignments; selecting region assignments from thereduced set of route assignments; and routing connections from the probepads to the micro-bumps according to the region assignments.
 19. Themethod of claim 18, wherein the reduced set of route assignments issubstantially less than all possible route assignments from the probepads to the target micro-bumps.